Defoaming emulsion

ABSTRACT

The defoaming activity of an aqueous defoaming emulsion containing an emulsifier, silica in fine particle form and methylpolysiloxanes is increased by incorporating into the emulsion 10 to 60 percent by weight, calculated on the total amount of siloxane in the emulsion, of organosilicon compounds of the general formula: WHEREIN X stands for -OR, R being hydrogen or alkyl of one to four carbon atoms, n has a value of 1.8 to 2.0 and m has a value from 0.02 to 0.33.

United States Patent Koerner [54] DEFOAMING EMULSION [72] Inventor:Glitz Koerner, Essen, Germany [7 3] Assignee: Tb. Goldscbmidt AG, Essen,Germany [22] Filed: Feb. 10, 1970 [21] Appl. No.: 10,281

[30] Foreign Application Priority Data March 22, 1969 Germany ..P 19 14684.0

[51] Int. Cl. ..B0ld 17/00 [58] Field of Search ..252/358, 321

[56] References Cited UNITED STATES PATENTS 3,455,839 7/1969 Rauner..252/32i FOREIGN PATENTS OR APPLICATIONS 1,067,003 3/1960 Germany..252/32l 1 51 Sept. 12,1972

Primary Examiner-John D. Welsh Attorney-McGlew and Toren [57] ABSTRACTwherein X stands for -OR, R being hydrogen or alkyl of one to fourcarbon atoms, n has a value of 1.8 to 2.0 and m has a value from 0.02 to0.33.

1 Claim, No Drawings DEFOAMING EMULSION FIELD OF THE INVENTION Theinvention relates to defoaming emulsions which comprise water,emulsifier, methylpolysiloxane and silica in fine particle form.

BACKGROUND INFORMATION AND PRIOR ART German patent 1,067,003 discloses adefoaming emulsion which essentially consists of water, emulsifier,methylpolysiloxane and silica in fine particle form. The silicone oil ofthe emulsion composition of this German patent is a predominantly lineardimethylpolysiloxane with terminal trimethylsiloxy groups. A typicalformulation for a prior art defoaming emulsion of this nature is asfollows:

54.2 parts by weight of water 30.0 parts by weight of methylpolysiloxane1.5 parts by weight of silicaaerogel 6 parts by weight ofpolyethyleneglycolmonostearate, and

8.3 parts by weight of sorbitemonostearate These known emulsions,however, are not fully satisfactory in respect to their defoaming effectand primarily in regard to their stability. Another well knowndisadvantage of the known emulsions is that they have a relatively highviscosity and thus are not sufficiently flowable. This disadvantage isparticularly pronounced if the emulsion has a relatively highconcentration, for example if the concentration is 30 to 50 percent ofaerosil enriched methylsiliconeoils. The impaired flowability of theemulsions makes it difficult to supply them in exact dosages anddilution of the emulsions is not always feasible or in any eventconnected with considerable difficulties. For these reasons such priorart emulsions are frequently not suitable as defoamers in aqueoussystems.

SUMMARY OF THE INVENTION It is a primary object of the present inventionto provide a defoaming emulsion, to wit an emulsion capable ofdestroying foam, which overcomes the disadvantages of the prior artemulsion formulations and which exhibits superior defoaming activity.

It is also an object of the invention to provide defoaming emulsions ofthe indicated kind which have satisfactory flowability and stabilitycharacteristics and are suitable for destroying foams in aqueoussystems.

Generally it is an object of the invention to improve on the art ofdefoaming emulsions as presently practiced.

Briefly and in accordance with this invention it has surprisingly beenfound that the defoaming activity of the prior art defoaming emulsionsis significantly improved if the emulsion is admixed with certainpredetermined organosilicon compounds.

It has thus been ascertained that emulsions of the indicated kind areimparted with superior characteristics if the emulsion contains 10 to 60percent by weight, calculated on the total amount of siloxane in theemulsion, of compounds of the general formula:

( H3) i f-(n +111) wherein X stands for the group OR in which R ishydrogen or alkyl of one to four carbon atoms, n has a value of from 1.8to 2.0 and m has a value of 0.02 to 0.33.

The stability of the emulsion is significantly increased by the additionof the compounds of formula 1 above. Moreover, the defoaming action ofthe emulsion is considerably improved. Emulsions of high concentrationsremain flowable and can be readily diluted with water. Furthermore, awide variety of emulsifiers may be used in the emulsions while, bycontrast, in the prior art emulsions the choice of emulsifiers isrelatively restricted.

Examples of organosilicon compounds to be incorporated in the emulsionsystem and being embraced by formula 1 above are for example compoundsof the formula F RO- s1-0-1R CH3 9 wherein R has the above meaning and phas a value of 10 to 100.

Another example of suitable compounds embraced by the general formulaare the compounds of formula l R b Moreover, compounds of the formulaare suitable for the inventive purpose. In the compounds of formula IV,q has a value of from 4 to 15 and r has a value of from 1 to 50.

It should be stated in this context that it was certainly surprisingthat the presence of the indicated compounds does in fact improve thecharacteristics and properties of the defoaming emulsions since thecompounds proper exhibit very slight defoaming activity only.

The inventive defoaming emulsion may for example have the followinggeneral composition:

10 to 55 percent by weight of oily phase 30 to 88.5 percent by weight ofwater, and

1.5 to 20 percent by weight of emulsifier or emulsifier mixture.

The oily phase may then have the following composition:

3 to 10 percent by weight of silica in finely distributed form(preferably pyrogenic silica) and to 97 percent by weight of siloxanemixture consisting of a. 10 to 60 percent by weight of a siloxane inaccordance with the invention and corresponding to formula I, and

b. 40 to 90 percent by weight of a polydimethylsiloxane which isendblocked with trimethylsiloxy groups. The polydimethylsiloxane shouldhave a viscosity of 50 to 5,000 cP, preferably 100 to 500 cP.

The emulsifier mixture consists advantageously of a hydrophobic and ahydrophilic component. Thus the HLB-value of the first component may besmaller than 6, while the HLB-value of the second component may begreater than 12. Suitable hydrophobic emulsifiers are carboxylic acidesters or fatty acid esters of multivalent alcohols as, for example, thestearic acid ester of glycols, glycerine or sorbite as well as higherfatty alcohols or the addition products of a few moles ethyleneoxide tothese fatty alcohols, fatty acids or similar compounds with activehydrogen atoms.

In respect to the hydrophilic emulsifiers, the addition products oflarger amounts of ethyleneoxide to the aforementioned products aresuitable. Thus, for example, the addition products of to 100 moles ofethyleneoxide to fatty alcohols are suitable. However, anionactiveemulsifiers, such as sodiumlaurylsulphate orsodiumdodecylbenzenesulphonate are also suitable for the indicatedpurpose.

The invention will now be described by several examples it beingunderstood, however, that these examples are given by way ofillustration and not by way of limitation and that many changes may beeffected without affecting in any way the scope and spirit of theappended claims.

The examples disclose the preparation and properties of the emulsionsand also include comparison of the properties with those of knownemulsions.

EXAMPLE I Defoaming emulsions composed of 10 percent by weight of oilyphase and 2 percent by weight of an emulsifier mixture of an HLB-valueof 4.9 were prepared. The composition of the oily phase is indicated inthe following Table I. The emulsifier mixture consisted of fattyalcohols or their polyethyleneglycolethers.

The defoaming or foam destroying activity was tested with a 0.1 percentaqueous solution ofa mixture of sodiumdodecylebenzenesulphonate andpolyethyleneglycolfattyalcoholether. For this purpose, 6 liter ofoil-free air per minute were conducted through l,000 ml of the tensidesolution at C. This was performed in a 2 liter measuring cylinder bymeans of a glass frit having the porosity l. A foam was formed in thismanner. When the foam had reached a volume of 1 liter, the air supplywas interrupted by removal of the frit from the measuring cylinder. 2.5ml of the defoaming emulsion which had previously been diluted withwater in the ratio 1:4 were then added. This corresponds to 50 ppm(parts per million) of oily phase. The dilution of the defoamingemulsion was effected with cold distilled water by adding the water inpor- 6O The numerical values obtained as a result of the tests aretabulated in Table I.

The table clearly indicates that the emulsion prepared in accordancewith the invention has a superior defoaming action if compared with thedefoaming action of the emulsions devoid of the inventive addition ofcompounds of formula I. The table furthermore indicates that thestability of the inventive emulsion is improved.

TABLE] siloxane of methylthc siliconc uemsil Defoaming Actionemulsionformula oil I 3 5 I030 I000 stability lll l000 cP min. min.min.min. min. ml n=6/b=3/ R=C.,H 5 I30 40 20 30 20 unstable min. 10 85 5 2O30 30 20 570 unstable l7.5 77.5 5 20 20 50 50 530 stable 27.5 67.5 5 2020 6O 60 330 stable 37.5 57.5 5 2O 20 20 30 270 stable 47.5 47.5 5 20 2020 40 340 stable 57.5 37.5 5 20 20 2O 20 340 stable 67.5 27.5 5 20 20 50360 stable 77.5 17.5 5 2O 20 20 60 26 stable min. 85.0 I00 5 20 20 30 6027 stable min. 95.0 5 20 20 20 320 21.5 stable min.

EXAMPLEZ Defoaming emulsions were prepared containing 50 percent byweight of oily phase and 14 percent by weight of an emulsifier mixture.The active substance has the following composition:

46.25 percent by weight of methylsilicone oil 46.25 percent by weight ofmethylsilicone oil 7.5 percent by weight of finely distributed pyrogenicsilica 37 percent by weight of methylsilicone oil 100 c? 37 percent byweight of methylsilicone oil 1,000

6 percent by weight of finely distributed pyrogenic silica 20 percent byweight of a siloxane of formula 111 wherein It will thus be noted thatthe formulation (a) above did not contain one of the inventivecompounds.

A mixture of polyethyleneglycolmonostearate and glycerinemonostearatewith an HLB-value of 12 was used for emulsifying purposes.

The emulsion obtained according to (a) above is no longer flowable andcannot be diluted with water. Moreover, it does not exhibit anydefoaming action. By contrast, the emulsion obtained pursuant to (b)above has a high defoaming activity and good flowabilitycharacteristics. The emulsion (b) can be readily diluted 6 with waterand can be directly used for defoaming (anon-sap without prior dilutionwith water.

What is claimed is:

l. A defoaming emulsion consisting essentially of to 55 percent byweight of an oily phase, 30 to 88.5 per- 5 cent by weight of water a d1,5 t by weight f wherein X stands for OR in which R is hydrogen oremulsifier or emulsifier mixture, said oily phase essenalkyl Of one tofour Carbon atoms, has a Value Of rom tially consisting of 3 to 10percent by weight of silica in to and has a Value Of from I0 and fineparticle form and 90 to 97 percent by weight of a 40 to 90 pefifem 9)weight of polydimethylsiloxane siloxane mixture, said siloxane mixturein turn essenelldbkfcked Wlth mmethylslmxy groups and having a tiallyconsisting of 10 to 60 percent of an organosilicon "scoslty of betweenabout 50 to 5,000 compound of the general formula:

